Unconventional well testing: a brief overview

The definition as well as the economic viability of the most suitable development strategy of a hydrocarbon reservoir mainly depend on the quantity and type of fluids, and on well productivity. Well testing, consisting in measuring the pressure variations induced in the reservoir during hydrocarbon production, has been used to assess fluid nature and well potential for decades, especially in exploration and appraisal scenarios. Today’s industry drivers for formation evaluation methodologies demand safe, environmentally friendly, and cost effective test procedures due to more stringent environmental regulations aimed at reducing emissions of greenhouse gases and hence restricting flaring of hydrocarbons produced during a test as well as the need for reducing operating costs – even more so with current oil prices. Different methods have been proposed or resuscitated over the last years, such as wireline formation tests, closed chamber tests, production/reinjection tests, injection tests and harmonic pulse test, as viable alternatives to conventional well testing. In this paper an insight is provided on wireline formation tests, injection testing and harmonic pulse testing to illustrate how testing techniques are evolving in the oil industry. The first one is a sort of mini test of the formation. The second methodology is one of the most promising methodologies to replace traditional well testing in reservoir characterization, but it does not offer the possibility of sampling formation fluids and thus is complementary to the previous one. The third one gives the same information of a conventional test, except for initial pressure, without significantly altering field operations thus it is well suited for monitoring production and storage wells.